Manufacture of incandescent electric lamps



App! 23, 1935. o. H. BIGGS ET AL MANUFACTURE OF INCANDBSCEN'T' ELECTR IC LAMPS April 23, 1935. O H BIGGS ET AL 1,999,014

MANUFACTURE OF INCANDESCEN'I ELECTRIC LAMPS Filed Jan. 21, 1931 2 Sheets-Sheet 2 INVENTORS. W BY M 5,

Patented Apr. 23, 1935 1,999,014

MANUFACTURE OF INCANDESCENT ELECTRIC LAIHPS Orrick H. Biggs, Beverly, and Lewis E. Cobb,

Marblehead, Mass., assignors to Hygrade Sylvatrga Corporation, a corporation of Massachuse Application January 21, 1931, Serial No. 510,110

6 Claims. (01. 91-70) This invention relates to incandescent electric Fig. is a side view illustrating a later step lamps and to methods of making them. n he m h An object of the invention is to provide the Fig. 6 is a side elevation showing another emenvelope of a lamp or similar hollow article with bodiment of the invention; and 5 a spray-coating of refractory translucent mate- Fig. 7 is a similar view illustrating a somewhat 5 'rial, over a predetermined localized area on the difierent arrangement embodying features of this interior of the article, in such a manner that the invention. edge of the coating provides a sharply defined According to the method DrOVided y this linear boundary between the coated and uncoated vention the coating material is sprayed on the 10 portions. inner surface of a portion only of the lamp, and 10 It is a common practice to etch or frost the the spray is very definitely controlled at the outer surface of the bowl portion of an electric margin of the coated area. It usuallyis preferlamp bulb to produce what is commonly known able to produce a relatively clear line of demarcaas a white bowl effect. In other words, this tion between the coated and uncoated areas, and part of the bulb is no longer clear and transparent the invention provides an apparatus with which 15 but is made translucent so that the glare is rethis result can be accomplished. As above indiduced and the lamp gives a softer and more difcated, it is usually desirable to coat only the fused light. This effect, also, is sometimes rounded end portion or bo l o the p bulb. obtained by coating the bowl externally with some this portion being indicated approximately by kind of a translucent material. Both of these the white area 2 in Figs. 1 and 2, and the cone 3 20 methods, however, are objectionable in that the and neck 4 of the bulb are left clear or uncoated. outer surface of the bulb thereby is rendered In some cases, 'however, it is desirable to coat sufiiciently rough to cause dust and dirt to cling the cone or skirt portion 3 and to leave the bowl 2 to it, thus reducing the illumination afforded by uncoated, a. lamp so treated often being referred the lamp. This is particularly true if the frosted to, as a skirt coated lamp. This invention pro- 25 or coated area becomes moistened at all with oil vides means for accomplishing this result also. or with dust of a sooty nature, as frequently The coating material used may be of any suitable appens in factories and industrial plants. nature, such for example, as those materials here- This fact has been recognized heretofore and toforev used for internal coatings. They should '30 attempts have been made to frost or coat the be capable of producing ahighly refractory transinside of the bulb. The frosting operation when lucent coating so that the presence of the coating performed internally is too expensive to be pracon the inner surface of the bulb will not materially tical, at least by present methods, and the coatreduce the life of the lamp or adversely affect its ing process has proved to be so difficult to control operation in any way. A typical coating comthat it has never gone into practical use, so far position consists essentially of water glass (sodium 35 as we are aware. silicate), water, and pigment. The present invention deals with this problem A convenient form of apparatus for producing and it aims to d e a thoroughly at s t ry white bowl effects according to this method is solution for it. illustrated in Fig. 1. It comprises a rotating 40 The nature of the invention will be readily head 5 having spring fingers 6 to grip the lamp 40 understood from the following description when bulb, and mechanism enclosed in the casing l for read in connection with the accompanying drawrevolving the head and the lamp around apings, and the novel features will be particularly proximately the axis of the lamp bulb. The neck pointed out in' the appended claims. of the lamp is steadied during this operation by In the drawings, three rolls 8 which engage the outer surface of 45 Figure l is a perspective view of an apparatus the neck and are supportedon a bracket 9. The embodying features of this invention, and decoating material preferably is applied by a spray signed for. use in practicing the method of this gun In which may be, of any suitable type, the invention; particular gun shown being of a common com- Fig. 2 is a similar view on a larger scale but mercial form. It includes a control lever or 50 showing only the lamp bulb and spray gun; trigger I 2, a relatively long shank l3 to reach Figs. 3 and flare plan and perspective views. well into the lamp bulb, and a spray nozzle M. ,a sprayv nozzle equipped with a This nozzle includes opposed air outlets l5, Fig. 4, ed in accordance with this inlocated at opposite sides of another outlet I6 for vention; the paint or other coating material. This is the 55 usual arrangement and it produces a fan-like sp y.

In using this apparatus the spray'nozzle is inserted in the bulb in approximately the position shown in Figs. 1 and 2, and the spray is turned on while the bulb is revolved by the head 5. Preferably the nozzle is advanced along substantially the path indicated by the dotted line H, Fig. 2, and is moved back and forth in this path several times during the spraying of a single bulb so that the entire inner surface of the bowl will be covered. This traversing movement may be produced either by hand or by automatic machinery, as desired.

As above indicated, it usually is preferable to have the coated portion 'of the bulb separated sharply from the uncoated area. The nature of the spray is such that it will not produce a sufficiently clear edge bounding the coated area, but we have found that such an edge can be produced by equipping the. spray nozzle with a shield such as that shown at l8. This shield may consist of sheet metal bent as shown, and including a split clamp l9 for securing it on the shank l3 of the spray gun. It is so shaped as to intercept or cut off one edge of the fan-shaped-spray sharply. With this arrangement, therefore, it is possible so to control the spray that the coated area will be terminated by a. fairly definite edge or margin.

The coating material intercepted by the shield 88 tends to collect on the shield and run down to the lower edge and drop off. In order to prevent this action we have bent over the lower edge of the shield, as shown-at 2b, to form a trough extending along this edge which serves to catch and hold such material. It will be understood that the period of time required to coat an individual bulb is very short indeed, so that this trough is not required to hold any great volume of liquid before it is withdrawn from the bulb, the spray first being shut ofi.

In using those coating materials which we have tried the best results are produced by heating the bulb during the spraying operation, and a burner is indicated diagrammatically at 2 I, Fig. -1, for this purpose. The heat causes the spray to dry on the glass surface almost as soon as it strikes it. If a water glass paint or coating material of the character above described is used, the heat has the effect of converting the coating into a very refractory deposit which neither affects adversely the operation of the lamp nor is itself adversely affected by such operation. It is contemplated, however, that some kinds of coating material may make this expedient unnecessary.

After the spraying operation has been completed and the bulb has been removed from the rotating head 5, it will be found that small particles of the spraystill adhere to the cone and neck of the bulb. We find, however, that these particles can be removed by washing or flushing the inner surface of the bulb with water. This operation may be performed by placing the bulb over a washing nozzle 22, Fig-.15, of a common form. The water issues from the holes in this nozzle at a considerable velocity in the form of a spray which has sufficientforce to wash away the small particles of coating material which adhere to the cone and neck of the bulb, but does not remove any material coating.

An arrangement better suited to automatic operation is illustrated in Fig. 6 in which the spray part of the white bowl gun I3 is mounted in an upright position, this gun being of the same construction as that shown in Figs. 1 to 4,-inclusive. It is equipped, however, with a shield 24 which is secured on the shank 13 of the spray gun by a clamp .25. This shield cuts ofl the edge of the spray in the same manner as does the shield l8 so that the spray at the margin of the coated area is definitely controlled. The small proportion of the coating material which strikes the surface of the shield 2i and runs down the inner surface of the shield is carried away by a tube 26 which extends along the shank I3 of the spray gun and empties into an annular trough 21 secured to the gun at the base of the shank I3. A rubber tube 28 drains this overflow from the trough 21. The side edges of the shield are slightly rolled to guide the drip into the tube 26.

An apparatus suitable for skirt coating lam bulbs is shown in Fig. '7. It includes a spray gun like that shown in Figs. 1 to 4, mounted in an upright position, and equipped with a shield 30 which is shaped to cut oil the upper edge of the fanlike spray instead of cutting off the lower edge, as does the shield 24. The shield 80 is equipped with a clamp 3| by means of which it is secured in the desired position on the spray gun. It will be clear from an inspection of Fig. '7 that in this arrangement the spray is confined t0 the skirt portion of the lamp, the bowl portion being left substantially clear.

In using both of the arrangements shown in Figs. 6 and 7 the lamp should be heated, as shown for example in Fig. 1. It will be understood, also, that the lamp and nozzle are relatively revolved in using both the arrangements shown in Figs. 6 and 7. Also, that the lamp may be washed afterwards in substantially the manner illustrated in Fig. 5 to remove any loose coating material.

We have found in practice that the invention provides an entirely satisfactory means for producing a white bowl effect, for skirt coating, or for internally coating any specified area of a lamp bulb and either leaving the remaining area clear or coating it with. a different color. The finished product meets the demands of the trade and item be produced at an entirely reason- .able expense.

bulb with a refractory translucent coating on a restricted area of the inner surface of the bulb, which comprises inserting spray nozzle with a shield positioned to intercept a predetermined portion of the spray within the bulb,v rotating the bulb and spray nozzle relatively to each I other, and diverting the excess spray material away from contact with the bulb.

2. The method of making an electric lamp bulb with a refractory translucent coating on a predetermined restricted area of the inner surface of the bulb, which comprises inserting a spray nozzle with a shield within the bulb with nozzle and shield positioned-to project a fanlike spray on a strip only of said restricted area,

the spray being projected at an angle to the longitudinal axis of the bulb and bein intercepted by the shield to out 01f the spray sharply at one edge while diverting excess spray material away from contact with the bulb, and rotating the bulb and spray nozzle relatively to each other to complete the coating of said restricted area.

3, The method of making an electric lamp bulb with a refractory translucent coating, which comprises selecting a restricted area on the inner surface of the bulb to be coated, inserting a spray nozzle with a shield into the bulb with the nozzle and the shield positioned to project the spraymaterial on only a strip of said selected area while diverting excess spray material away from contact with the bulb, and rotating said spray nozzle and bulb relatively to each other to complete the coating of said restricted area.

4. The method according to claim 1 in which the bulb is heated over said restricted area while said restricted area is being sprayed.

5. An electric lamp bulb having a coating of sprayed translucent refractory material on a predetermined restricted area of the inner surface of the bulb the boundary of the restricted area being substantially uniform and determined during the spraying as set forth in claim 1.

6. The product of the process of claim 1 comprising a lamp bulb with a spherical bowl portion and a reduced neck portion the inner surface of the bowl having a refractory translucent coating over a predetermined restricted area on the inner surface of the bowl the boundary line of demarcation between said restricted coated area of the bowl and the uncoated area having a sharpness characteristic of the said process.

ORRICK H. BIGGS. LEWIS E. COBB. 

